/*********************************************************************************
 *      Copyright:  (C) 2025 LingYun IoT System Studio
 *                  All rights reserved.
 *
 *       Filename:  pipe.c
 *    Description:  This file 
 *                 
 *        Version:  1.0.0(18/03/25)
 *         Author:  Guo Wenxue <guowenxue@gmail.com>
 *      ChangeLog:  1, Release initial version on "18/03/25 19:50:38"
 *                 
 ********************************************************************************/

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>

#define MSG_STR "This message is from parent: Hello, child process！"

int main(int argc, char **argv)
{
	int				pipe_fd[2];
	int				rv;
	int				pid;
	char			buf[512];
	int				wstatus;

	if( pipe(pipe_fd) < 0)
	{
		printf("Create pipe failure: %s \n",strerror);
		return -1;
	}

	if( (pid =fork()) < 0)
	{
		printf("Create child process failure: %s\n",strerror(errno));
		return -2;
	}
else if(pid ==0)
{
	/* child process close write endpoint, then read data parent process  */
	close(pipe_fd[1]);

	memset(buf, 0, sizeof(buf));
	rv = read(pipe_fd[0], buf, sizeof(buf));
	if(rv < 0)
	{
		printf("Child process read from pipe failure: %s\n",strerror(errno));
		return -3;
	}
	
	printf("Child process read %d bytes data from pipe: \"%s\"\n",rv,buf);
	return 0;
}

/* parent process close read endpoint ,then write data to child process */

close(pipe_fd[0]);
if( write(pipe_fd[1], MSG_STR, strlen(MSG_STR))< 0)
{
	printf("Parent process write data to pipe failure: %s\n",strerror(errno));
	return -3;
}

printf("Parent start wait child process exit...\n");
wait(&wstatus);

return 0;
}
